In increasingly complex reproduction or copier machines, customers demand an ever increasing amount of options, while at the same time demanding lower cost and greater reliability. This is particularly true in the low copy volume copier market, which most copiers are sold. Until recently, small size has been achieved by leaving out features commonly found in larger, more expensive machines. Now, customers regularly demand the same features in smaller sizes and at lower cost.
Of particular interest in smaller copiers is the provision of duplex copying. Duplex copying, i.e. copying on both sides of a single sheet, presents significant problems in any copying machine since it entails the handling of paper which has already been processed and is less than perfect. Additionally, a large amount of work has been done in the area of providing a workable paper path for use in such machines. Further, it is desirable to make any operations in such copying machines as automatic as possible with a minimum of operator intervention. In small copiers these problems are increased since there is a limited amount of space for paper paths and a limited amount of automation possible due to the need for limitations in cost.
Not every consumer wishes to pay for duplex operation. These products must appeal to the entire range of small copier purchasers, some of whom will prefer models that have fewer options at lower prices. At the same time, it would be highly desirable that a consumer could easily retrofit a flexible machine for duplex operation by providing the duplex operation as a simple add on component. In this manner, the consumer will not be required to purchase a new reproduction machine when he chooses to add duplex operation. Additionally, the duplex operation should bring added advantages to the consumer who, after all, will not use the duplex operation for every copy made. Accordingly, the add on duplex component should also be highly capable of operation in simplex mode.
In duplex machines heretofore known, dedicated duplex tray, has been required as part of the process of inverting documents for receiving an image on a second side of a copysheet. In such a machine, a copysheet having an image on one side is fed into the tray from the normal copysheet path and then refed back to the copysheet path. By converting the trailing edge of the copysheet to the leading edge of the copysheet, the copysheet is turned over in the normal paper path, and an image may be placed on the second side of the copysheet. It will be appreciated that an inverting tray takes up room in the machine that then cannot be used for other purposes. Further the process of depositing and then refeeding the sheet is one that is difficult to perform reliably in the degraded condition of the image bearing copysheet. Additionally, the refeeding mechanisms add expense and take up space in the machine associated with the inverter tray.
In addition to duplex copying inversion, a non-inverting copysheet return pass is required if a two color copying or image merging capability is to be provided. In such an operation, a copysheet receives a first image, say, for example using black toner or inking material, and must be returned to the processor to receive a second image over the first image using a separate inking material, for example, red toner. Alternatively, a second image in any color, including black, may be merged onto a single side of a copysheet with a previously presented copysheet. This involves a copysheet handling operation similar to duplexing except that no inversion is required. It would be desirable to make use of existing copysheet paths or copysheet to accomplish color copying or image merging.
During duplex operation it is desirable to use a trayless path, i.e. a path which passes the copysheets bearing an image on a first side directly back to the reproduction processor to avoid the requirement of depositing the copysheets into a duplex tray for storage and subsequently refeeding them into the reproduction processor. A trayless path is preferred because stacking sheets in a duplex tray and subsequently refeeding the sheets out from the tray takes time and reduces productivity. One alternative which would produce a satisfactory result would be the provision of a bottom feeder in the duplex tray. This solution is not economically attractive for lost cost copiers. While it is possible to use only the trayless path in certain short runs, e.g. a small number of copies per document, for greater numbers, the duplex tray is used exclusively. However, the requirements of small copier users are such that they generally do not use the duplex mode for particularly long runs, and it would be desirable to take advantage of the trayless path, with its improved productivity and reliability with respect to the duplex tray, as much as possible. Accordingly, an arrangement which uses a combination of the duplex tray and trayless path would be highly advantageous. Of course, the choice of paths must be automatic with the machine.
Additionally, the use of the trayless path enables the small copier to use certain copying schemes that are otherwise very expensive, including two up simplex document to duplex copysheet copying. For vacuum corrugating bottom feeders it is possible to feed out from the bottom and into the top of the duplex tray to gain a similar advantage, however, such feeders are very expensive. Particularly, copying processes which make the most efficient use of the reproduction processor possible require the fast return of copysheets for duplex copying, which is possible with the trayless path.
For duplex operation for documents presented in N-1 sequence, it is preferred that the machine controller knows the number of documents in a job to be run, or at least whether the number is odd or even. Otherwise, when the job is run for an odd number of pages to be copied, the last odd page, which is the first document to be scanned, will appear on the reverse of the last copysheet as opposed to being copied simplex, as should occur. If this happens, the copy of the first document page which was the last copied, will not have an image on its reverse side as normally desired by an operator. Larger machines may be provided with recirculating document handlers which can count the documents without running the processor, and return the documents to the input position with the number of documents known and ready to start the copying job. However, recirculating document handlers are usually very expensive, and are not economically attractive for use on smaller copiers at the present time. Accordingly, it would be desirable for a document feeder normally used with such copiers to accommodate a counting function, and advise the machine operator to return the counted documents to the input side of the feeder. It would also be desirable if the operator who knows the number of documents in the job would enter the number to the controller to avoid the time consuming count.
As noted it is desirable for the components needed for the duplex function of a machine to serve in other capacities in addition to the duplex mode. Accordingly, a duplex tray should also be useful for holding a supply of paper for first side copying, and using the duplex copysheet handling devices to pass blank copysheets to the reproduction processor. For use of the duplex tray in this mode, it is desirable that the presence of paper in the duplex tray be detected, its size sensed, and the information be transmitted to the operator via a display on the control panel. For duplex operations, it would be desirable to sense the presence of copysheets, and register the copysheets in a known position as they are passed to the duplex tray. Additionally, as no paper should be in the duplex tray prior to duplex operations, it would be desirable for a paper detection operation to be performed at this time.
A module as contemplated will be provided with a sliding drawer holding the duplex tray. This is contemplated since it requires a minimum amount of room in an arrangement with the reproduction processor. Accordingly, the tray must be provided with paper guides to support paper held therein against movement when the drawer is closed. It would also be desirable that the paper guides provided be as easily adjustable for the operator as possible to accommodate a number of different paper sizes during the paper supply operations, as well as support copysheets received in the duplex tray during duplex operation. Thus, paper guides in the present invention should not require operator adjustment when changing amount different sizes of standard paper in either mode of operation. Additionally, operator access to the copysheet paths contained in the module for jam clearance and servicing, should be provided, small size of the module not withstanding.
For small copier products it is desirable that the drivers of any of the functions of the machine must perform multiple functions. Thus for example, a single motor could drive the copysheet tray feeder, duplex tray feeder, switch cams, enable deflectors, etc. The problem is compounded when it is realized that many of these functions must be isolated from one another, i.e., the separate functions must not be allowed to operate simultaneously.